Luis is 5 times as old as Jessica and is also 16 years older than Jessica. How old is Jessica?
Solution: We can use the given information to write down two equations that describe the ages of Luis and Jessica. Let Luis's current age be $l$ and Jessica's current age be $j$ $l = 5j$ $l = j + 16$ Now we have two independent equations, and we can solve for our two unknowns. Since we are looking for $j$ , and both of our equations have $l$ alone on one side, this is a convenient time to use elimination. Subtracting the second equation from the first equation, we get: $0 =$ $5j$ $-$ $ (j + 16)$ which combines the information about $j$ from both of our original equations. Solving for $j$ , we get: $4 j = 16$ $j = 4$.